Optically active amines (hereinafter sometimes referred to as chiral amines) are compounds of importance extensively used in the fields of fine chemicals, pharmaceuticals, agrochemicals and the like.
As a method for producing optically active amines from ketone and amine, the followings are known:
a method in which ketone and amine are subjected to reductive amination for production of an amine compound, and the amine compound is optically resolved using an optically resolving agent (for example, chiral camphorsulfonic acid etc.), and
a method in which ketone and optically active α-methylbenzylamine are subjected to reductive amination for production of an amine compound having a benzyl group, and then the amine compound is decomposed into an optically active amine. For example, the patent literature 1 discloses a method which involves hydrogenating 5-acetonyl-2-methoxybenzenesulfonamide and (R)-(+)-α-methylbenzylamine in the presence of a platinum catalyst (platinum oxide) into 2R,1R-methoxy-5-[2-(1-methylbenzylamino)propyl]benzenesulfonamide, and then subjecting the resulting compound to catalytic reduction to obtain (R)-methoxy-5-(2-aminopropyl)benzenesulfonamide.
As a more advantageous method for producing optically active amines, a method involving use of a chiral metal catalyst for asymmetric reduction of imine compounds obtained from ketone and amine is known. For example, the patent literature 2 discloses a method for producing optically active amines, the method involving asymmetric transfer hydrogenation of ketone and amine in the presence of a hydrogen donor and a catalyst. In this literature, as the catalyst, there is used, for example, a metal catalyst produced by reaction of a chiral or achiral, phosphine or diphosphine ligand with a metal pre-complex (for example, [(S—BINAP)RuCl2(DMF)x], [(R-TolBINAP)RuCl2(DMF)x], [Ir(C8H12)Cl]2, [Ir(C8H14)2Cl]2+R-TolBINAP, etc.). Further, the patent literature 3 discloses a method for producing optically active amines, the method involving asymmetric transfer hydrogenation of imine compounds in the presence of a hydrogen donor and a chiral ruthenium complex represented by the following formula:
(wherein the ring A represents benzene or p-cymene, and Ar represents tolyl, 2,4,6-trimethylphenyl or 1-naphthyl).
Furthermore, the nonpatent literature 1 discloses a method for producing optically active amines, the method involving asymmetric transfer hydrogenation of ketone and ammonium formate in the presence of an iridium catalyst (for example, a catalyst formed of (1R,2R)-1,2-diphenyl-1,2-ethylenediamine and [Ir(C8H14)2Cl]2/2 or [Ir(C5Me5)Cl2]2/2).
Such conventional methods, however, are not necessarily satisfying. For example, the method of the nonpatent literature 1, probably due to relatively high temperature of 60 to 85° C. required as its reaction condition, has a disadvantage that besides amine compounds, large amounts of byproducts such as alcohol compounds and N-formylamine compounds are obtained. Moreover, it is generally difficult to obtain good optical yields in the case of simple chain ketones, in which each of the carbon atoms adjacent to the carbonyl group constitutes an alkyl group or the like (nonpatent literatures 1 and 2).    Patent Literature 1: JP-B 6-6565    Patent Literature 2: JP-A 2004-537588    Patent Literature 3: WO 97/20789 pamphlet    Non Patent Literature 1: Angew. Chem. Int. Ed, 2003, 42, 5472-5474    Non Patent Literature 2: Angew. Chem. Int. Ed, 2001, 40, 3425-3427